1. Field of the Invention
The present invention relates generally to a pressure sensor and more particularly, to an oil pressure sensor.
2. Description of the Related Art
FIG. 1 and FIGS. 2A and 2B show an oil pressure sensor of a prior art. The sensor, denoted by reference numeral 1, mainly comprises a housing 10, a pressure sensing unit 11, a first signal generator 13, a second signal generator 15, a first signal outputting member 17 and a second signal outputting member 19. The pressure sensing unit 11 includes a top cover 112 having an oil inlet 111, a base case 113 connected with and located beneath the top cover 112, a flexible diaphragm 114 disposed between the top cover 112 and the base case 113, an intermediate cap 115, a pusher 116 and a coil spring 117.
When the oil is introduced into the sensor through the oil inlet 111, the center portion of the flexible diaphragm 114 will downwardly deform due to the oil pressure and then push the intermediate cap 115 and in turn the pusher 116 to make the intermediate cap 115 and the pusher 116 compress the coil spring 117 and at the same time make the pusher 116 drive a crank 131 of the first signal generator 13 to swing and scrape on a coil member 133. As a result, an oil pressure signal is outputted through the first signal outputting member 17 that is electrically connected with the first signal generator 13. In the mean time, as shown in FIG. 3, a straight rod 151 of the second signal generator 15 is pressed to move downwardly, such that the oil pressure signal is outputted through the second signal outputting member 19 that is electrically connected with second signal generator 15.
The above-mentioned conventional oil pressure sensor has several drawbacks that will adversely affect the accuracy of the oil pressure signal. For example, because the spiral structure of the coil spring 117 can not uniformly receive the force exerted by the pusher 116, i.e. the coil spring 117 can not uniformly support the pusher 116 under movement, the pusher 116 tends to inclinedly and unevenly push the first and second signal generators 13 and 15, resulting in inaccurate oil pressure signal output. Further, the crank 131 of the first signal generator 13 is contacted with the pusher 116 by its bent portion 135 merely. This contact mechanism is barely stable and the bottom surface of the pusher 116 tends to be worn due to the scrape of the bent portion 135 of the crank 131, causing inaccurate oil pressure signal output. Further more, since the crank 131 and the straight rod 151 need to be contacted to the bottom surface of the pusher 116 at one time, both of them can not be simultaneously stopped at the geometric center of the bottom surface of the pusher, which is the optimum force-applying position of the pusher 116, thereby affecting the accuracy of the oil pressure signal.